Cod sursa(job #3173485)

Utilizator Radu_MocanasuMocanasu Radu Radu_Mocanasu Data 22 noiembrie 2023 22:18:27
Problema Pairs Scor 0
Compilator cpp-64 Status done
Runda Arhiva de probleme Marime 1.37 kb
#include <bits/stdc++.h>
#define NMAX  1000000
using namespace std;
ifstream fin("pairs.in");
ofstream fout("pairs.out");
bitset <NMAX + 5> c;
int fp[NMAX + 5];
int mp[NMAX + 5];
void ciur(){
    c[2] = 1;
    for(int i = 2; i <= NMAX; i += 2){
        c[i] = 1;
        fp[i] = 2;
    }
    for(int i = 3; i * 2 <= NMAX; i++){
        if(!c[i]){
            for(int j = i; j <= NMAX; j += i){
                fp[j] = i;
                c[j] = 1;
            }
        }
    }
}
int nrdp(int n){
    int s = 0;
    while(n > 1){
        int k = 0,f = fp[n];
        while(n % f == 0){
            n /= f;
            k++;
        }
        if(k > 2) return 0;
        s++;
    }
    return s;
}

int main()
{
    int n,i,d,x;
    ciur();
    fin >> n;
    for(i = 1; i <= n; i++){
        fin >> x;
        for(d = 2; d * d < x; d++){
            if(x % d == 0){
                if(nrdp(d))
                    mp[d]++;
                if(nrdp(x / d))
                    mp[x / d]++;
            }
        }
        if(d * d == x && nrdp(d)) mp[d]++;
        if(nrdp(x)) mp[x]++;
    }
    long long rez = 1LL * n * (n - 1) / 2;
    for(i = 2; i <= NMAX; i++){
        if(!mp[i]) continue;
        if(nrdp(i) % 2 == 1) rez -= mp[i] * (mp[i] - 1) / 2;
        else rez += mp[i] * (mp[i] - 1) / 2;
    }
    fout << rez;
    return 0;
}